Malbim: (a) If he would have been lacking for his meal, she would need to tell him right away - However, "the feast in his house was like the king's feast"; he did not notice what was missing. (b) "Naval was jolly" - she did not want to upset him and mar his Simchah. (c) "He was very drunk" - she feared to arouse his anger amidst his intoxication, lest he harm her.